Anything from several thousands of dollars to hundreds of millions of dollars can go into the development and production of big-budget Hollywood movies - and with that kind of money being utilised it's easy to expect the end result to be flawless. That's not always the case, however - far from it, in fact.
Like any line of work, there is bound to be human error involved - especially when it comes to movies that have been made over the course of a couple of years, with thousands of hours of manpower and hundreds of people involved.
With that in mind, mistakes are often made in Hollywood. Whether it is gaping, unforgivable errors or errors that you have to actively look for in order to spot them, movies are littered with factual errors, historically inaccurate errors, spelling mistakes and many other kinds of boo-boos - and they're fun to acknowledge, whether it's simply something you enjoy looking out for, whether it's so you can vent your frustration at the perpetrator or just because it makes you feel better about your own mistakes.
This article will look at some errors that were made in some of Hollywood's biggest offerings. Here are fifteen movie mistakes you didn't notice.
15 "Stegasaurus" (Jurassic Park)
Remember that famous scene in the 1993 classic Jurassic Park when Dennis Nedry shut down some of the park's security and surveillance in order to steal dinosaur embryos from the cold storage and smuggle them off the island? Well, as he was removing said embryos, the names of the dinosaurs in question were all clearly labelled next to their respective embryos.
You'd think Jurassic Park's scientists would be able to spell the names of dinosaurs correctly, given that they were capable of bringing them back to life after 65 million years, right? Wrong! "Stegosaurus" was incorrectly spelt "Stegasaurus" (an "a" where an "o" should have been). Oh dear.
14 The Orca's ID Number Changes (Jaws)
In the 1975 classic Jaws, the three main characters - Quint, Brody and Hooper - set out on Quint's boat to hunt the titular shark that had been causing so much trouble around Amity Island. The boat - known as the Orca - was ultimately wrecked by the shark as it ferociously and relentlessly attacked the trio, ultimately killing Quint.
As well as its colloquial name, it also had an official ID number - kind of like how a car has a license plate. However, the Orca's ID number inexplicably changed during the course of the movie. At one stage, its ID was "MS 15 LF", then the "MS" disappeared leaving only "15 LF" and, at other points in the movie, it appeared as though there was no number visible at all.
13 That's Not Marty Driving! (Back To The Future)
During the scene in 1985's Back to the Future when the Libyan terrorists come to kill Doc Brown for stealing plutonium from them, a car chase occurs between the terrorists themselves (in their little camper van) and Doc's pal Marty McFly (in the classic DeLorean time machine) - except Marty clearly isn't the one driving.
On a number of occasions in far shots, the man driving the DeLorean is quite obviously a stunt driver and not Michael J. Fox's character at all. In fact, quite a few times during the movie - when both Fox and Christopher Lloyd's Doc Brown were meant to be driving - the stunt driver can clearly be seen.
12 A Visible Cameraman (Harry Potter & The Chamber Of Secrets)
2002 saw the release of the second instalment in the Harry Potter movie franchise - Harry Potter and the Chamber of Secrets. By the time this movie came around, the titular hero and the troublesome Draco Malfoy were practically sworn enemies already and, when the time came for the students of Hogwarts to start training in magical duels, it was always going to happen that they would cross wands.
Harry gets the better of Draco and the other students rejoice but, during the evil blonde kid's defeat, a kneeling cameraman can clearly be seen on the left hand side of the screen.
11 The Man In Blue Jeans (Raiders Of The Lost Ark)
In 1981, the first Indiana Jones movie was released, simply called Raiders of the Lost Ark (later marketed as Indiana Jones and the Raiders of the Lost Ark). In a scene filmed in Tunisia that was doubling as Cairo in the 1930s, the people behind the movie went to extreme lengths to ensure it looked like the Egyptian capital in that era - even going as far as removing more than 300 television antennas from the backdrops of particular scene. However, some modern visuals still slipped in unnoticed.
For instance, while Indy is sitting with the little monkey having a drink, a white man in blue jeans and a grey T-shirt can clearly be seen nonchalantly wandering on the set in the background.
10 "Nameco Bandai" (The Avengers)
The Avengers was the highest-grossing movie of 2012 and currently sits as the third highest-grossing movie of all time - but it wasn't without its mistakes. Of course, the movie itself contained numerous errors - as do all movies - but one of the most glaring mistakes in the Avengers movie actually came in the credits.
Thanks to Tony Stark's name-dropping of the video game "Galaga", Marvel Studios had to credit the company who developed it - that being "Namco Bandai". However, the credits had it incorrectly spelt as "Nameco Bandai". This only occurred in the cinematic release, however, as the issue was fixed in time for the home release of the movie.
9 A Visible Gas Cylinder (Gladiator)
For a movie that won five Academy Awards and was nominated for an additional seven, 2000's Gladiator was absolutely teaming with glaring errors. Crew members appeared in crowd shots and the appearance of sets changed during scenes, but arguably the worst mistake was during the re-enactment of the Battle of Carthage in the Colosseum.
After the dust settles around a fallen chariot, a gas cylinder that was used to cause it to flip over can quite clearly be seen. Aside from the fact that it was meant to be impact caused by an opponent that toppled the chariot, gas cylinders certainly weren't around in the year 180 AD!
8 Kid Blocks His Ears Before A Gunshot (North By Northwest)
The 1959 classic Alfred Hitchcock spy thriller North By Northwest is a movie about mistaken identity which sees Cary Grant's Roger O. Thornhill pursued across the United States by agents of a mysterious organisation, as they believe he a man named Kaplan who is trying to interfere in their plans to smuggle out microfilm containing government secrets.
At Mount Rushmore's visitor centre, Thornhill is confronted as part of a ruse by Eva Marie Saint's Eve Kendall. She fires blanks at him to make others think he has been shot. A child performing as an extra can be seen in the background blocking his ears prior to the gun going off, when he really shouldn't have known it was going to happen at all.
7 A Cowboy On A Pirate Ship? (Pirates Of The Caribbean: The Curse Of The Black Pearl)
"On deck, you scabrous dogs!" Those are the words uttered by Johnny Depp's Captain Jack Sparrow in the final scene of 2003's Pirates of the Caribbean: The Curse of the Black Pearl. It's all very pirate-esque and seems in keeping with the general theme and feel of the franchise as a whole - but there's something a little odd about this particular scene.
Just as Sparrow says those words, the camera pans around and an unwelcome guest appears on board - a crew member in a cowboy hat! While the idea of cowboys and pirates mingling with each other is pretty cool, it certainly wasn't intentional in this case.
6 Why Pay That Much Money? (X-Men: First Class)
2011's X-Men: First Class was the first movie in the X-Men franchise that depicted the younger versions of the likes of Charles Xavier (Professor X) and Erik Lensherr (Magneto) - played by James McAvoy and Michael Fassbender, respectively. Some of the movie shows Xavier at the end of his university days at Oxford and one such scene - in a bar on campus - contains a rather weird error.
Xavier orders a pint of bitter, a brandy and a cola - for himself, a girl he is chatting up and his stepsister Raven - and pays with a £5 note. The movie is set in 1962, when £5 was worth the equivalent of around £100 - or $150 - and yet the barman neither batted an eyelid or offered change!
5 Bullet Holes Before The Gun Has Fired (Pulp Fiction)
Quentin Tarantino is famous for his attention to detail in his movies, so it is something of a surprise that this blatant error made it into his 1994 classic mobster movie Pulp Fiction. It's in the scene known as "The Bonnie Situation", when John Travolta's Vincent Vega and Samuel L. Jackson's Jules Winnfield are at Brett's apartment.
A man (credited simply as Man #4) played by Robert Arquette bursts out of the bathroom, firing wildly at them. He misses with every shot and they subsequently kill him, then they look at the bullet holes in the wall behind them. The weird thing? The bullet holes were already there before the man had fired a single shot.
4 The Fake Baby (American Sniper)
American Sniper was one of the best movies of 2014 - but, for some people at least, the whole thing was ruined by one scene with an incredibly obviously fake baby (well, it's obvious once you've been told it's fake at the very least - go take a look!). The scene shows Bradley Cooper's Chris Kyle and his wife - Sienna Miller's Taya Renae Kyle - passing their baby back and forth. And it's awful.
It's so fake and so incorrectly weighted that the actors look uncomfortable using it. Cooper even uses his own thumb to animate its arm (see the arrow above)! While it was undoubtedly a mistake to have used it, director Clint Eastwood claimed that one real baby they were going to use was sick with a fever and another didn't show up. Still, you'd think they'd have found another!
3 Lake Wissota (Titanic)
James Cameron's epic 1997 romantic disaster movie Titanic was critically praised almost universally. It was nominated for fourteen Academy Awards and won no less than eleven. While this was heavily due to the acting, directing, cinematography and all of the art that goes into movie production, its historical accuracy was also a major factor.
However, there's a glaring historical error in the scene when Leonardo DiCaprio's Jack Dawson is trying to coax Kate Winslet's Rose DeWitt Bukater back on to the ship's deck when she was threatening to jump off. He gets talking to her and refers to how he and his father had been ice-fishing at Lake Wissota - a man-made lake that, in reality, wasn't actually built until five years after the Titanic had sunk.
2 The White Van (Braveheart)
Like Gladiator before it on this list, 1995's Braveheart can be forgiven for a mistake like the odd crew member creeping onto the screen, given that the large scale battles and scenes with large crowds make them harder to spot - but this particular mistake in the Scottish historical drama is simply unforgivable.
During one particular battle sequence, a white van can clearly be seen in the background of a shot with horses charging forward. Bearing in mind this movie is set in the 13th century, you would think the people behind the movie would have been more careful. In spite of the error, the movie still earned five Academy Awards from an impressive ten nominations.
1 The Amazing Healing Vest (X-Men: The Last Stand)
2006's X-Men: The Last Stand saw Magneto putting together an army - his Brotherhood of Mutants - to combat those responsible for developing a "cure" for the mutant gene. In one particular scene, he can be seen with them in a forest, hiding out and addressing them while they prepare to make their move on their targets at Worthington Labs.
Hugh Jackman's Wolverine turns up - as you would expect - and is spotted by Magneto's pawns. One of those pawns, Spike, attacks him by throwing spiky bone-like projectiles at him. Eventually, they meet in close-combat, resulting in Spike dying and Wolverine being wounded - with two spikes stuck in his stomach. His white vest is pierced and blood is showing on both wounds. Wolverine's healing factor obviously allowed him to heal, but what is more remarkable is that the blood and rips on the vest are gone just a scene later. Oops!